Gear shock disc collar orientation

[Hradec]

Hi, 

I replaced the shock disks on my nose gear and the collar that secures the stack has a bevel that was on top facing fwd. Now I am doing the main landing gear disks and on one gear the collar had the bevel facing down and aft. The other gear had the bevel facing up.

What is the correct orientation of the collar bevel?

Thanks

Glenn

64 m20e. SN 311

 

 

[Marc L.]

Here is the retrofit kit instructions.  This should help

 

SBM20-139A 2.pdf

[Hradec]

It doesnt mention the orientation of the collar 

[Vance Harral]

I know this isn't the answer you want to hear, but I don't think the orientation matters in practice.

The IPC illustration for the main gear doesn't display the bevel on the collar.  The IPC illustration of the nose gear may show the bevel, but it's not clear, and doesn't seem to match where the bevel actually is (see attachment).  The service manual doesn't mention the bevel, it just refers to installing "the collar".  And as you note, the retrofit kit doesn't mention the bevel either.

I just looked through some old photos I took of measuring the gap with respect to shock disk replacement, and I can see the bevel in the photos on one side of the mains (bevel up) and I can't see it in the photos of the other side (bevel down, or not there at all).  I can't see any obstruction that the bevel would clear, nor can I see any reason the collar would be easier to remove or re-install based on the orientation of the bevel.

The only thing I can think of is that perhaps the bevel is designed to snug against the bolt head.  But I have a sneaking suspicion the beveled collar was actually designed for some application, and just happened to be convenient for use in our airplanes.

 

[Shadrach]

My understanding is the that the orientation is not important with the exception of the nose gear, where the collar can sometimes be flipped to attain the correct gear geometry (castor).

[PT20J]

Why not just ask Frank Crawford at Mooney?

[EricJ]

1 hour ago, Shadrach said:

My understanding is the that the orientation is not important with the exception of the nose gear, where the collar can sometimes be flipped to attain the correct gear geometry (castor).

Yes, the nose gear collar has more gap from the fastener on one side than the other, so you can adjust the gap/compression a little bit by flipping the collar.

If the instructions on the bevels are so ambiguous it likely doesn't matter how they're oriented unless there's an obvious clearance issue with something.   A gear swing usually reveals any issues.

[jamesm]

I just had mine changed this year by my IA I didn't get see the whole thing being done from start to finish but I had changed the mains about 2000's year mark . Nose gear pucks were right at the limits and the pucks/disks/discs were older than me (10/66) had me by a couple of months. for some reason right main was just inside the limits  and left main was ok. Not sure how right main was more compressed the the left main pucks. should be go to for a while now.

[Kelpro999]

 If I remember correctly, the bevel provides clearance away from the structure welds. Even upgrades from Firestone disks required different collars for some reason.